Car Stuttering (7MGE)

[chedderknight]

I have this weird problem, I"ll try and discribe it as best as I can, its a 1991 non-turbo automatic, it begins to stutter around 2 to 3000 rpms and onwards, by stuttering I mean the car sounds like it can't breathe right and you hear popping coming from my exhuast and engine, and when i force it to accelerate it feels like my engine is gonna pop out from under the car at any moment, now whats odd about this is that it only happens at night, and when i put it in park and rev it, it sounds fine, only in drive does this problem occur, I cleaned the filter, change my manifold gasket, still same problem, any ideas? its gets really frustrating because I cant really speed up on the freeway. I'll try to get a sound clip as soon as I can. thanks

 

[ShagsSupra]

have you done a compression check?

My NA Auto did somthing like them when I blew my HG, it was the pre syptoms..

Check for smoke too.

If not that could just not be getting enough fuel or air, run a scan on it see it its throwing codes.

 

[mrnickleye]

Possibly the spark plug wires breaking down and not firing the plugs properly.

 

[Topher E]

mis-alinment in the driveliine can also be caused by nutral drops. Have you ever done those?

 

[chedderknight]

I"ll check the compression today, I wonder now and then if my AFM is just breaking down on me or so, and it could be the spark plugs, its worth a shot, not sure about the driveline, can you elaborate more on that subject?

oh if it helps any, I bought this car in January of this year (2005), before i bought the car the guy let it sit in his front yard for about a year, give or take.

 

[Nick M]

Possibly the spark plug wires breaking down and not firing the plugs properly.

Yep, that sounds like non stock tune up parts, or old tune up parts that need replacing.

 

[Steve_N]

Agreed-

Change out the spark plugs, wires, dist. cap & rotor

 

[supraman7mgte]

just curious,have you washed the motor/engine bay recently? it sounds like water in the spark plug holes too.But yeah,check the spark plugs and change the wires if they are suspect,Definately do a compression check

 

[chedderknight]

Last time I cleaned the engine would be back in march, used about 3 cans of engine degreaser and 2 cans of engine brite.

Couldn't get a compression test, friend didn't have his kit on him, but I'm thinking it could be the spark plugs + wires, they are in need of changing anyway, owner before just did enough for it to run so he could sell it. So I'mma try that, also some more info, this only started happening after I installed the HKS N/A Catback exhuast could that also be a factor? though it still puzzles me to why the stuttering occurs at night and not during the day or evening, any ideas on that?

 

[tubbie]

Bad afm.....

 

[Steve_N]

Yea, could be a bad Solar lumanescent sensor on the AFM.


..... J/K.... Couldn't resist.


Honestly could be the AFM but I think it may be the Cap & rotor are just that worn. With the cooler night air comes condensation that could interfer with spark contact between the cap, rotor or even bad wires.

Good luck

 

[chedderknight]

how do you check if the AFM is bad? its gotten to the point I dont drive the supra at night and just borrow my brothers Maxima

 

[Steve_N]

Check for code 31 http://www.cygnusx1.net/supra/techtip/engineerrorcodes.html

 

[chedderknight]

new update on the problem, its gotten bad now, it has a rough idle, goes from 1000 - 500 rpms, and now when I'm going about 40 and its revving between 2-3000 rpms it suddenly drops causing the car to seriusly lag, anyone here live in the LA area that could help me out?

 

[tubbie]

How to test AFM....
Unplug the AFM connector. Drive around. Notice how bad it drives. Now plug the connector back in. Notice how it drives. Are they the same problem? if they are, bad AFM. If not, still possible bad AFM, but may be other things too.

 

[Steve_N]

Well I assume that you checked & tested everything above & it turned out ok. Only other things I can think of would be faulty FPR, Fuel Pump, or cloged fuel filter.

 

[chedderknight]

i check the diagnostics and I"m getting a code 32, so now that narrows it down,I'mma try the AFM connector tomorrow, would it better to replace the afm with one from a junkyard or get it refurbished (is that even possible?) or to fix the circuitry somehow?

 

[Steve_N]

Your best bet would be to get one from a SM member in the for sale section. You can get them refurbished also.

 

[mrnickleye]

It seems that you are very intent on replacing that AFM. That is an expensive part, so better to do the ignition stuff first. It probably needs the stuff anyway. I manage a smog shop up here in the Mojave Desert, and I see way more problems with wires, plugs, cap and rotor, O2 sensors and cat converters, than any cars AFM.

Fuel system can be easily checked.

Eliminate the 'routine' maintenance things before replacing high dollar things. Then get back with us.